Often in a wellbore more than one formation or zone is intersected for production and/or injection of a fluid. Typically, in multiple zone wells a lower zone is completed first. This completion may include gravel pack, stand alone screen, expandable screen casing and perforation, or a combination of apparatus and methods. At this stage of the drilling operation it is often desired to test the zone utilizing drillstem testing (DST) to determine certain characteristics of the selected zone and the viability for production and/or injection. Drillstem testing at this stage provides information that can be utilized for decisions regarding further completion of the well.
After completion of the lower zone, the lower zone may be “killed” or isolated utilizing formation isolation valves so that the upper zone can be completed. Once the upper zone is completed it is often desired to test the upper zone for same reasons as testing of the lower zone. This completion and testing process is performed through several trips in the wellbore in addition to those performed regarding the completion and testing of the first or lower zone.
Drillstem testing is utilized to determine data related to, but not limited to, the productive capacity, pressure, and permeability of the selected formation. These tests are usually conducted with a downhole shut-in tool that allows the well to be opened and closed at the bottom of the wellbore. One or more pressure gauges are customarily mounted in the DST tool and are read and interpreted after the test is completed. It is also often desirable to obtain a sample of the fluid produced from a zone without producing the fluid to the surface, the sample being collected downhole. The data obtained from these drillstem tests facilitate educated decisions regarding further completion of the well.
Although drillstem testing of formations may reduce the total cost of drilling and completing a well, the drill stem testing process is also costly and time consuming. The current process of testing multiple zones in a well includes (well utilizing perforation and gravel packing): 1) trip into hole to perforate first zone; 2) trip into hole to gravel pack/complete lower zone; 3) trip into hole and drillstem test the lower zone, kill the well after the test; 4) trip into hole to perforate upper zone; 5) trip into hole to gravel pack/complete upper zone; 6) trip into hole and drillstem test the upper zone, kill the well after the test; 7) trip into the hole with the drillstem tester to configure the hole and test commingled production from the lower and upper zones. Various methods may be utilized to complete the production zones, however, the prior art system typically requires three (3) trips in the wellbore to perform two independent zone tests and a commingled test. This prior art method, while effective, is time consuming and costly.
It is a desire to provide a multiple zone testing system that permits a single trip into the hole to test multiple zones. It is a further desire to provide multiple zone testing system that facilitates separate testing of individual zones and commingled flow testing of multiple zones.